The Addendum was produced byTriData, which is based in Arlington, Virg. It takes into account information that has come into the public domain since the submission of the original panel report, including the Cook Counseling Center records of Seung-Hui Cho that were discovered in 2009.

According to the Governor, the Addendum corrects or clarifies the facts of the panel report, but does not make any changes to the conclusions or recommendations of the panel, most of which were implemented in 2008.

The third chapter of the report is the single notable exception to the overall format of the Addendum. "Chapter III- Revised Timeline of Events" has been rewritten to include more detailed information and more precise times of events leading up to, during, and after the shootings on April 16, 2007. There is no distinction in the timeline between information included in the original document and information that has been added or revised.According to a N.Y. Times article , the new report reveals several disturbing facts about the actions of Virginia Tech administrators, including:

Students who were initially locked down at West Ambler Johnston residence hall, where the spree began, were later released from the building by the police and allowed to attend their 9 a.m. classes. Two of those students then went to class in Norris Hall, where they were slain by Seung-Hi Cho, the shooter..

The university president's office was locked down about 30 min before a formal warning was issued campuswide. And, at least two members of the Policy Group managing the crisis alerted their own families about the first two shootings in the residence hall more than 90 min. before the Group warned the rest of the campus.